Les Donald H, Sheridan Donna J
Department of Biological Sciences, The University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, 53201.
Am J Bot. 1990 Apr;77(4):453-465. doi: 10.1002/j.1537-2197.1990.tb13576.x.
Morphologically heterophyllous species of Potamogeton also commonly display biochemical heterophylly with respect to flavonoid compounds. Generally, floating leaves contain an assortment of flavonoids, whereas submersed leaves often exhibit reduced flavonoid profiles. In strictly submersed (homophyllous) species, two patterns occur. Linear-leaved species have few flavonoids and their biochemical profiles resemble those of submersed leaves of heterophyllous species. Broad-leaved homophyllous species possess flavonoid profiles more similar to those of the floating leaves of heterophyllous species. Numerical analysis of these chemical data is consistent with phylogenetic relationships within the genus derived independently on the basis of morphological and chromosomal data. Glycoflavones, which are probably maintained in floating leaves because of their UV filtering ability, exhibit the most pronounced biochemical heterophylly in Potamogeton. The lack of glycoflavones in submersed leaves of heterophyllous species and in linear-leaved homophyllous species is attributable to the ability of naturally colored water to significantly absorb harmful UV radiation. These observations provide strong support for earlier hypotheses suggesting the importance of flavonoid evolution in the conquest of exposed terrestrial habitats by plants.
眼子菜属形态上具有异形叶的物种通常在黄酮类化合物方面也表现出生化异形叶性。一般来说，漂浮叶含有多种黄酮类化合物，而沉水叶的黄酮类化合物含量通常较少。在严格沉水（同形叶）的物种中，有两种模式。线性叶物种的黄酮类化合物较少，其生化特征与异形叶物种的沉水叶相似。阔叶同形叶物种的黄酮类化合物特征与异形叶物种的漂浮叶更为相似。这些化学数据的数值分析与基于形态学和染色体数据独立得出的该属系统发育关系一致。糖基黄酮可能因其紫外线过滤能力而在漂浮叶中得以保留，在眼子菜属中表现出最明显的生化异形叶性。异形叶物种的沉水叶和线性叶同形叶物种中缺乏糖基黄酮，这归因于天然有色水体能够显著吸收有害紫外线辐射。这些观察结果为早期假说提供了有力支持，这些假说表明黄酮类化合物进化在植物征服暴露的陆地生境中的重要性。
